Reasonable values for Me-Me, H-Me and Me-H A1,3-strain have been evaluated by molecular mechanics calculations on differently substituted methylenecyclohexanes (5.46-6.75, 1.03 and 0.71 kcal mol, respectively). The chair-to-chair inversion barrier of methylenecyclohexanes has also been calculated. Methods are described for the thermodynamic and for the kinetic preparation of acylhydrazones of 2,6-dialkylcyclohexanones. A PMR analysis of the cis and trans-2,6-dimethylcyclohexanone semicarbazones has allowed the determination of the preferred conformers. The results agree with MM results on model hydrocarbons. Finally, a MM study of hydrocarbon models for the antibiotics isocycloheximide, cycloheximide and neocycloheximide points out to a decrease in stability on going from the former to the later, in agreement with the reported experimental results. © 1985.